Nonvolatile memory devices, e.g., electronically erasable programmable read only memories (EEPROMs) or flash memories may store data even when power is turned off, and further, stored data may be erased therefrom and new data may be programmed thereto. Nonvolatile memory devices may be used in semiconductor products, e.g., storage media for mobile devices or portable memory sticks, etc.
Recently, with the trend toward smaller semiconductor products, nonvolatile memory devices used in the semiconductor products have become more highly integrated. For example, three-dimensional nonvolatile memory devices may have a higher degree of integration in a plane compared to two-dimensional nonvolatile memory devices. Further, three-dimensional nonvolatile memory devices may be manufactured using silicon-on-insulator (SOI) substrates or nanowire structures.
In three-dimensional nonvolatile memory devices, a channel layer may not be directly connected to a substrate. Thus, in three-dimensional nonvolatile memory devices, it may be more difficult to erase data by applying a body bias to a substrate, unlike in conventional two-dimensional nonvolatile memory devices. In this regard, data may be erased by applying a negative voltage to a control gate electrode. However, this may lower the reliability of a tunneling insulating layer.